Numerical investigations of unsteady viscous flow in centrifugal pumps were conducted in this paper. Verification of numerical approach was done. Hydraulic components of the pump were modernized with the purpose to improve their acoustic characteristics. Modernization was held on the base of isotropic turbulence noise measuring techniques. Results were confirmed by experiment. Pressure pulsations were studied in a flow between rotating impeller and stator for initial and improved flowing parts. As a result of numerical research, various impellers with different blade outlet angles were designed. During optimization, the optimal blade outlet angle was found, which provides increased vibroacoustic characteristics while maintaining a high level of efficiency.
Axial-flow pumps, in addition to providing high anti-cavitation properties, must have high anti-erosion properties to ensure the required lifetime of the pump. Erosion damage of surfaces occurs when the net positive suction head (NPSH) significantly exceeds its critical value. The object of the study in this article is the axial-flow pump with a specific speed of 600 in two alternatives: № 1 and № 2. By analysis of the flow in the impeller blade systems, the ratio value between the NPSH, which ensures the absence of erosion, and the NPSH3, at which pump operational failure occurs, was determined. Impeller variant № 1 did not provide the required ratio. Impeller variant № 2 had higher cavitation qualities, and the required ratio was achieved for it. Energy, cavitation, and erosion characteristics of the axial-flow pump with impeller № 2 in rotational frequency n = 2000 rpm were investigated. Easily breakable paint coatings were used for the accelerated study of cavitation erosion. The experiment was carried out at three different flow rates and confirmed the assumptions made—the pump with impeller № 2 was not affected by cavitation erosion at the optimum flow rate. Patterns of erosion zones were accompanied by calculations of vapor zones in the impeller. At flow rates less than the optimum, cavitation disruptions occurred and appeared behind the vapor region. As a result, the condition of ensuring erosion-free flow in the impeller of an axial pump with a specific speed of 600 was obtained, ensuring the ratio NPSH/NPSH3 > 2.5. Recommendations on designing of erosion-free flow part of the axial pump impeller were also obtained.
The issue of ensuring high energy efficiency of high-power pumps is relevant, since an in-crease in hydraulic efficiency of such pump flow parts leads to significant savings in the operation costs. Introduction of digital simulation technologies for the viscous fluid flow makes it possible to optimize geometry of the flow path elements at the design stage and predict pump characteristics with sufficient degree of accuracy. The main elements influencing characteristics of the multi-stage pumps flow parts include impellers and taps. Most often, vane and channel diffusers are used as retractors in the multistage pumps. Results of designing and optimizing flow parts of the low speed multistage centrifugal pump with both types of diffusers are presented, as well as predictive characteristics of pumps obtained using the computational fluid dynamics methods. Hydraulic efficiency of a stage with the channel-type guide (optimized version) is by 0.3 % higher than the efficiency of a stage with the vane-type guide. Both optimized flow paths have a non-sinking nature of pressure characteristics in the low flow region. The pump stage with the channel-type guide has a smaller radial overall dimension than the stage with the vane diffuser = 0.88) and higher design manufacturability. It was found that the most preferable option for the feed electric pump stage with the ns = 85 speed factor is the optimized flow path with the channel-type diffuser
The results are presented of numerical and experimental research of fluid flow in the flow path of a torque flow pump with specific speed ns ;: 55. The 3D methods of CFD have been shown to allow for predicting energy characteristics of this type of pumps with a sufficient accuracy. According to the results of flow visualization the work process has been analysed and conclusions drawn to enhance TFP efficiency.
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